The long-range objective of this research is the systematic identification and characterization of etiologically distinct subtypes of reading disability. The specific goals of the three-year program project are as follows: (1) to develop a test battery of highly reliable behavioral and electrophysiological measures that can be administered to a wide age-range of subjects without extensive pretraining and in a reasonable time period; (2) to administer this battery to a core sample of 150 reading-disabled and matched control children; (3) to identify subtypes of reading disability; and (4) to conduct a small-scale genetic linkage analysis. To test the validity of this typology, a shortened test battery will be administered to families of core subjects in a subsequent program project. The research is being conducted by four testing domains. Academic and Cognitive Abilities are being evaluated by a battery of standardized achievement, language, and intelligence tests. The Word Decoding Operations domain utilizes analyses of spelling errors, oral reading errors, and eye fixation patterns. Cerebral Specialization obtains measures of cortical evoked potentials to provide information on patterns of hemispheric dominance in processing different types of information. Finally, Genetic Linkage Analyses are conducted on a limited number of families whose members exhibit patterns of dominance inheritance. During Year Three, the final 75 core subjects will be tested and multivariate analyses of the combined data set will be undertaken.